package main

import (
	"fmt"
	"os"
)

type point struct {
	i,j int
}

var dirs = [4]point {
	{-1,0},{0,-1},{1,0},{0,1},
}

func (p point) add (r point) point {
	return point{p.i+r.i,p.j+r.j}
}

func (p point) at (grid [][]int ) (int,bool) {
	if p.i < 0 || p.i >= len(grid) {
		return 0,false
	}

	if p.j <0 || p.j >= len(grid[p.i]) {
		return 0,false
	}
	return grid[p.i][p.j],true
}

func walk(maze [][]int,start,end point) [][]int {
	steps := make([][]int ,len(maze))
	for i := range maze {
		steps[i] = make([]int,len(maze[i]))
	}
	Q := []point{start}
	for len(Q) > 0 {
		cur := Q[0]
		Q = Q[1:]
		if cur == end {
			break
		}
		for _,dir := range dirs {
			next := cur.add(dir)

			//maze act next is 0
			//steps at next is 0
			//next != start
			val,ok := next.at(maze)
			if !ok || val == 1 {
				continue
			}
			val,ok = next.at(steps)
			if !ok || val != 0 {
				continue
			}

			if next == start {
				continue
			}

			curSteps,_ := cur.at(steps)
			steps[next.i][next.j] = curSteps+1

			Q = append(Q,next)
		}
	}

	return steps
}

func readMaze(filename string ) [][]int {
	file,err := os.Open(filename)
	if err != nil {
		panic(err)
	}

	var row,col int
	fmt.Fscanf(file,"%d %d",&row,&col)

	maze := make([][]int,row)
	for i:= range maze {
		maze[i] = make([]int,col)
		for j:=range maze[i] {
			fmt.Fscanf(file,"%d",&maze[i][j])
		}
	}
	return maze
}

func main() {
	maze := readMaze("maze/maze.in")
	for _,row := range maze {
		for _,val := range row {
			fmt.Printf("%d ",val)
		}
		fmt.Println()
	}
	steps := walk(maze,point{0,0},point{len(maze)-1,len(maze[0])-1})
	for _,row := range steps{
		for _,val := range row {
			fmt.Printf("%3d",val)
		}
		fmt.Println()
	}

}
